The fastest way to remove a virus depends on whether your computer still starts

If your computer starts normally, run a full scan with your built-in antivirus software or a free scanner like Malwarebytes. If it won't start, or if the virus blocks your antivirus from running, you will need to boot into Safe Mode or use a bootable scanner on a USB drive. The steps differ because a virus running in the background can prevent normal removal tools from working.

Start by identifying what is actually wrong. A slow computer, unexpected pop-ups, or programs that open on their own are common signs, but they can also mean a hardware problem or a legitimate program misbehaving. Before you assume a virus, check whether your hard drive is full, whether Windows Update is running in the background, or whether a program you recently installed is the culprit.

Key Takeaways

  • If your computer starts normally, open Windows Defender (built into Windows) or read Malwarebytes and run a full system scan before restarting.
  • If a virus blocks your antivirus from opening, restart your computer and press F8 or Shift+F8 during startup to enter Safe Mode, then run the scan from there.
  • A bootable antivirus USB (created on another computer) can scan and remove viruses even if Windows will not start at all.
  • After removal, change your passwords, check your browser homepage and search engine settings, and look for unfamiliar programs in your installed software list.

Running a full scan with Windows Defender or Malwarebytes

Windows Defender is already on your computer if you use Windows 10 or later. Open it by clicking the Windows Start button, typing "Windows Defender" or "Virus & threat protection," and pressing Enter. Click "Scan options," select "Full scan," and click "Scan now." A full scan takes 30 minutes to several hours depending on how much data you have. Let it finish without interrupting it.

If you prefer a second opinion or if Windows Defender misses something, read Malwarebytes from malwarebytes.com on another computer or on the same computer if it still works. The free version scans and removes threats. Install it, open the program, click the "Scan" tab, select "Threat Scan," and click "Start Scan." When the scan finishes, click "Quarantine" to remove anything it found. Restart your computer afterward.

Do not pay for a removal tool during a scan. Scareware — fake antivirus programs that claim your computer is infected and demand payment — is itself a common virus. Stick to Windows Defender, Malwarebytes, or Kaspersky Rescue Disk (described below).

Entering Safe Mode if the virus blocks normal scanning

Safe Mode starts Windows with only the essential programs running, which often prevents a virus from blocking your antivirus. On Windows 10 and 11, restart your computer. As it starts up, hold down the Shift key and click the power button, then click "Restart." Your computer will show a menu. Click "Troubleshoot," then "Advanced options," then "Startup Settings," then "Restart." When the list appears, press 4 or F4 to enter Safe Mode.

Once you are in Safe Mode, open Windows Defender or Malwarebytes and run a full scan the same way you would normally. Safe Mode limits what the virus can do while the scan runs. After the scan finishes and threats are removed, restart your computer normally.

If you cannot reach the menu or your computer will not start at all, you will need a bootable scanner instead.

Using a bootable antivirus USB when Windows will not start

A bootable scanner is a program on a USB drive that scans your computer before Windows even loads. You need another working computer to create it. On that computer, read Kaspersky Rescue Disk from kaspersky.com/downloads/rescue-disk or ESET SysRescue from eset.com/us/home/tools. Both are free. Insert a blank USB drive (at least 1 GB), open the downloaded file, and follow the instructions to write the scanner to the USB.

Insert the USB into the infected computer and restart it. As it starts, press Delete, F2, F12, or Esc (the key varies by computer) to enter the boot menu. Select the USB drive from the list. The scanner will start automatically. Let it scan your entire hard drive, which takes 30 minutes to an hour. When it finishes, remove the USB and restart normally.

If you do not know which key to press to enter the boot menu, restart the computer and watch the first screen carefully — it usually displays the key in small text at the bottom. If you miss it, restart and try again.

Cleaning up after virus removal

After a successful scan and removal, a virus may have left behind changes to your browser or installed unwanted programs. Open your web browser and check the homepage and search engine settings. In Chrome, click the three-line menu, go to "Settings," click "On startup," and make sure it is set to open a page you recognize. Check the search engine under "Search engine" and change it back to Google if it has been changed.

Open the Windows Start menu, type "Add or remove programs," and look through the list for anything you do not recognize or did not install yourself. Uninstall anything suspicious. Also check your browser extensions: in Chrome, click the three-line menu, go to "More tools," click "Extensions," and remove anything unfamiliar.

Change your passwords for email, banking, and other important accounts. Use a different computer if possible, because the virus may have captured your keystrokes. If you used the same password on multiple sites, change all of them.

Preventing future infections

Keep Windows and all your programs updated. Windows updates include security patches that close holes a virus could use. Click the Windows Start button, type "Check for updates," and click "Check for updates now." Install any updates offered and restart if prompted.

Be cautious with email attachments and downloads. Do not open an attachment from someone you do not know, and do not read files from websites that look suspicious or ask you to disable your antivirus. Viruses often spread through fake invoices, shipping notifications, or urgent-sounding messages that trick you into opening them.

Use a strong, unique password for your email account. Your email is the key to resetting passwords on other sites, so protecting it is critical. A strong password is at least 12 characters long and includes uppercase letters, lowercase letters, numbers, and symbols.

What to do if the virus returns or will not go away

If you have run multiple scans and the virus keeps coming back, it may be deeply embedded in your system or your computer may have a hardware problem. Try one more bootable scan with a different tool — if Kaspersky did not work, try ESET SysRescue, or vice versa. Different tools catch different viruses.

If the problem persists after two bootable scans, the virus may require professional removal or your computer may need to be reinstalled from scratch. A local computer repair shop can do this, or you can back up your important files and reinstall Windows yourself using a Windows installation USB (available from Microsoft's website). Reinstalling Windows removes everything and starts fresh, which always removes a virus, but you will lose any programs you installed.

Frequently Asked Questions

How do I know if my computer actually has a virus?

Common signs are unexpected pop-ups, a browser homepage that changed without your permission, programs opening on their own, or a noticeably slow computer. However, these can also be caused by a full hard drive, too many browser extensions, or a program running in the background. Run a scan with Windows Defender or Malwarebytes to know for certain.

Is it safe to use my computer while a scan is running?

You can use your computer, but the scan will run slower and take longer. It is better to start the scan and leave the computer alone until it finishes. If you need to use your computer, at least avoid opening many programs at once.

Do I need to pay for antivirus software to remove a virus?

No. Windows Defender is free and built in, and Malwarebytes has a free version that scans and removes threats. Kaspersky Rescue Disk and ESET SysRescue are also free. Paid antivirus software offers extra features, but you do not need to pay to remove an existing virus.

What if I cannot find the boot menu key for my computer?

Restart the computer and watch the first screen closely — the key is usually shown in small text at the bottom, often something like "Press F12 to enter boot menu." If you miss it, restart and try again. If you still cannot find it, search online for your computer's brand and model plus "boot menu key."

Can a virus spread to my phone or other devices?

Most computer viruses cannot infect phones or tablets because they run different operating systems. However, if a virus stole your passwords, someone could use them to log into your phone or other accounts. Change your passwords after removing a virus, and consider enabling two-factor authentication on important accounts for extra security.